Apparatus and methods for balancing a joint

ABSTRACT

A joint replacement balancing system which provides real-time feedback to a surgeon during a joint replacement surgery to assist the surgeon to balance a joint replacement. The joint replacement balancing system includes a non-transitory processor-readable medium storing code representing instructions to cause a processor to receive a signal from a joint balancing apparatus, determine if the joint replacement is out of balance, determine a corrective course of action to bring the joint into balance and generate and display to the surgeon during the joint replacement surgery a recommended corrective course of action to complete the joint replacement surgery.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/456,270, filed Jun. 28, 2019, which is acontinuation application of U.S. patent application Ser. No. 15/056,855,filed on Feb. 29, 2016, now U.S. Pat. No. 10,376,332, which is adivisional of U.S. patent application Ser. No. 13/230,583, filed on Sep.12, 2011, now U.S. Pat. No. 9,307,929, the entirety of this applicationis hereby incorporated by reference herein. Any and all applications forwhich a foreign or domestic priority claim is identified in theApplication Data Sheet as filed with the present application are herebyalso incorporated by reference under 37 CFR 1.57.

BACKGROUND

The embodiments described herein relate generally to apparatus andmethods for balancing an artificial joint, and more particularly toapparatus and methods for providing real-time feedback during aprocedure for balancing an artificial joint.

Traumatic, inflammatory, and degenerative disorders of joints can leadto severe pain and loss of mobility. One source of joint pain is relatedto the inflammation or degeneration of the cartilage and/or bone of ajoint, such as for example, arthritis. Bony contact or grinding ofdegenerated joint components can play a role in some pain syndromes.

One current standard of care to address the degenerative problems with ajoint is to replace all or part of the joint. By performing thissurgical procedure, the contact or grinding of the degenerated joint canbe stopped, thus stopping any potential pain generated as a resultthereof. Performing this surgical procedure, however, may also changethe range of motion of the replacement joint relative to both a healthyjoint and the degenerated joint. Because of the change in the range ofmotion of the joint, the surgeon performing the joint replacement mustbalance the joint accurately during the initial procedure to bothmaximize the range of motion of the joint, and to reduce the likelihoodof follow up procedures. If not properly balanced, the replacement jointcan be subject to, for example, excessive wear, instability andloosening.

Accordingly, a need exists for apparatus and methods to balance a jointduring a joint replacement procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a conventional joint replacement apparatus.

FIG. 2 is a functional block diagram of a joint balancing apparatusaccording to an embodiment.

FIG. 3 is a perspective view of a joint balancing apparatus according toan embodiment.

FIG. 4 is an exploded perspective view of the joint balancing apparatusshown in FIG. 3 .

FIG. 5 is a schematic view of a joint and joint balancing apparatusaccording to an embodiment in a first configuration.

FIG. 6 is a schematic illustration of the joint and the joint balancingapparatus shown in FIG. 5 in a second configuration.

FIG. 7 is a schematic illustration of a joint balancing apparatusaccording to an embodiment.

FIG. 8 is a schematic illustration of a joint balancing apparatusaccording to an embodiment.

FIG. 9 is a cross-sectional schematic illustration of atransducer/actuator of a joint balancing apparatus according to anembodiment in a first configuration.

FIG. 10 is a cross-sectional schematic illustration of thetransducer/actuator shown in FIG. 9 in a second configuration.

FIG. 11 is a flow chart of a method of balancing a joint using a jointbalancing apparatus according to an embodiment.

FIG. 12 is a flow chart associated with an algorithm according to anembodiment.

DETAILED DESCRIPTION

In some embodiments, an apparatus for balancing a joint includes a firstportion configured to be coupled to a first bony structure and a secondportion configured to be coupled between the first portion and a secondbony structure. The second bony structure is disposed opposite the firstbony structure. The apparatus further includes a transducer and/or anactuator coupled between the first portion and the second portion. Insome embodiments, the transducer is used to convert variousinputs/readings (e.g., force, pressure, rotation) to output signalsassociated with the apparatus. In some embodiments, the transducers canbe associated with actuators to respond to external signals and causemovement of the apparatus 2 as described herein. In some embodiments,the apparatus can have separate transducers and actuators or thetransducers and actuators can be part of the same component. In someembodiments, the transducer/actuator is a piezoelectric material, whichcan be configured as both a sensor/transducer and an actuator.

In some embodiments, a method for balancing a joint includes outputtinga signal including a first data set associated with at least one of aforce, a position, a displacement or a rotation associated with anapparatus. The apparatus is disposed between a first bony structure anda second bony structure, and includes a first portion configured to becoupled to the first bony structure, a second portion configured to bedisposed between the first portion and the second bony structure, and atransducer and/or an actuator disposed between the first portion and thesecond portion.

The method for balancing a joint further includes outputting a signalincluding a second data set, the second data set associated with atleast one of a force, a position, a displacement or a rotationassociated with the apparatus after the performance of at least a partof a surgical procedure. The surgical procedure is based at least inpart on a recommendation based on the first data set. The method furtherincludes moving, in response to the received signal, a movable portionof the transducer and/or actuator (or one or both of the first portionor the second portion of the apparatus). The movable portion of theactuator causes one of the first and second portion of the apparatus tomove with respect to the other of the first and second portion of theapparatus.

In some embodiments, a non-transitory processor-readable medium storescode representing instructions to cause a processor to receive a signalincluding a first data set associated with at least one of a force, aposition, a displacement or a rotation associated with an apparatus. Theapparatus is disposed between a first bony structure and a second bonystructure, and includes a first portion configured to be coupled to thefirst bony structure, a second portion configured to be disposed betweenthe first portion and the second bony structure, and a transducer and/oran actuator disposed between the first portion and the second portion.The non-transitory processor-readable medium further stores coderepresenting instructions to cause a processor to generate, based on thefirst data set, a recommended action to complete a surgical procedure,the generating occurring during the surgical procedure.

As used in this specification, the term “joint” includes any joint orlocation at which two or more bones are in close proximity, such as forexample, a knee joint, a shoulder joint, a hip joint, a spine or portionof a spine, an elbow joint, an ankle, and/or a patellofemoral joint. Asused in this specification, the term “bony structure” can include anybone, bone portion, and/or other bony structure associated with a joint,such as for example, a portion of a tibia, a portion of a femur, aportion of a humerus, a portion of a scapula, a portion of a pelvis, aportion of a vertebra, a portion of an ulna, or a portion of a talus.While a total joint arthroplasty is generally shown and described,unicompartmental and/or partial joint replacement is also contemplated.

As used in this specification, the words “proximal” and “distal” referto a location closer to and away from, respectively, a torso and/oranother location central to a body. Thus, for example, the end of afemur closer to the knee joint would be the distal end of the femur,while the end of the femur closer to the hip joint would be the proximalend of the femur.

As used in this specification, the singular forms “a,” “an” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, the term “a transducer” is intended to encompass asingle transducer or multiple transducers.

Conventional knee arthroplasty (i.e., joint replacement) involvesreplacement of some or all of the knee joint. FIG. 1 illustrates anartificial knee joint 150 including a tibial portion 155 coupled to aproximal end of a tibia T and a femoral portion 160 coupled to a distalportion of a femur F. An interface or contact portion 170 is disposedbetween the tibial portion 155 and the femoral portion 160. Theinterface portion 170 has a surface configured to slidingly nest withthe outer surface of the femoral portion 160 such that the knee joint isable to rotate through its natural range of motion. Connective tissue C(represented by dashed lines) maintains the femur F and tibia T in theappropriate relative position.

FIG. 2 is a functional block diagram of a joint balancing apparatus 100.Joint balancing apparatus 100 can be a temporary, permanent, orsemi-permanent implant configured to replace a joint and/or to providedata used to provide real-time feedback to a surgeon. The real-timefeedback can be used by the surgeon to properly balance the joint duringthe surgical procedure. Real-time feedback can include recommendedactions for completing a surgical procedure, such as for example, tomake a specific bone cut and/or 4 loosen or tighten one or moreconnective tissues associated with the joint. After the joint isbalanced, joint balancing apparatus 100 can be either completely orpartially replaced by a permanent replacement joint. In other words,either the entirety of joint balancing apparatus 100 or a portion ofjoint balancing apparatus 100 can be replaced, or joint balancingapparatus 100 can remain in place and can function as the permanentreplacement joint. Alternatively, an appropriate prosthesis/device thatcorrects the imbalance can be selected for implantation. Joint balancingapparatus 100 includes a first portion 102, a second portion 112, atransducer 108, and an intermediate portion 116. Transducer 108 can beoperatively coupled to a computer system CS. In some embodiments, jointbalancing apparatus 100 includes a separate actuator (not illustrated),operatively coupled to the computer system CS.

First portion 102 is configured to be coupled to a first bony structure(not shown in FIG. 2 ), such as a proximal portion of a tibia. In someembodiments, first portion 102 can be coupled to the first bonystructure substantially flush with the first bony structure. In suchembodiments, first portion 102 can be held in place by a temporary orpermanent adhesive, and/or another temporary or permanent fastener. Inother embodiments, first portion 102 can include a mount (not shown inFIG. 2 ) configured to extend from first portion 102 and into the firstbony structure. In such embodiments, the mount can be shaped tocorrespond to a cavity formed in the first bony structure. In someembodiments including the mount, the mount can be held in place by atemporary or permanent adhesive, by friction within the cavity, and/orby another temporary or permanent fastener. In some embodiments, themount can be permanently coupled to, and/or monolithically formed with,first portion 102. In other embodiments, the mount can be removablycoupled to first portion 102. In these embodiments, the mount can be afirst mount, and the first mount can be used during a balancingprocedure on a joint, and the first mount can be replaced by a secondmount, during and/or after the balancing procedure, the second mountconfigured to remain in the joint after the balancing procedure.

Second portion 112 is configured to be coupled between the first portionand a second bony structure (not shown in FIG. 2 ) such as a distalportion of a femur. In some embodiments, second portion 112 can beslidably coupled to the second bony structure. For example, secondportion 112 can move relative to the second bony structure and canmaintain a point of contact with the second bony structure, and thepoint of contact between the second bony structure and second portion112 can change as the first bony structure moves relative 5 to thesecond bony structure. In some embodiments, the second bony structurecan be in direct contact with second portion 112. In other of theseembodiments, a contact portion (not shown in FIG. 2 ) can be disposedbetween the second bony structure and second portion 112. In suchembodiments, the contact portion can be fixedly coupled to the secondbony structure or the second portion 112, and the contact portion can beslidably coupled to the other of the bony structure or the secondportion 112.

Intermediate portion 116 is configured to be disposed between firstportion 102 and second portion 112 and can be configured to restrict,limit, or otherwise define, the movement of first portion 102 relativeto second portion 112. Said another way, intermediate portion 116 candefine the ranges of motion of first portion 102 relative to secondportion 112. In some embodiments, the intermediate portion 116 can beone of a post, a bearing, or a gasket. In some embodiments, intermediateportion 116 can define an area between first portion 102 and secondportion 112, the area configured to include transducer/actuator 108.

Knee balancing apparatus 100 can include transducer 108 configured tooutput data associated with knee balancing apparatus 100 and itsinteraction with the joint in which it is positioned. Transducer 108 canbe disposed between first portion 102 and second portion 112. In someembodiments, transducer 108 can be disposed in an area between firstportion 102 and second portion 112 defined by intermediate portion 116.In some embodiments, transducer 108 can include a fixed portion coupledto one of first portion 102 or second portion 112, and can include amovable portion coupled to the other of first portion 102 or secondportion 112. In such embodiments, the movable portion of transducer 108can be movable relative to the fixed portion of transducer 108 andfunctions as an actuator (i.e., causes relative movement of firstportion 102 and second portion 112. In some embodiments, the fixedportion of transducer/actuator 108 can be fixedly coupled to one offirst portion 102 and second portion 112. In some embodiments, themovable portion of transducer/actuator 108 can be slidably coupled toone of first portion 102 and second portion 112. In some embodiments,transducer/actuator 108 can be a plurality of transducers/actuators 108.In some embodiments, transducer/actuator 108 can be embedded in theintermediate portion 116. In some embodiments transducer 108 andactuator are arranged as a single component. In some embodiments, thetransducer and the actuator are separate components.

Transducer 108 can be configured to record measurements and output data,such as for example, force data, position data, displacement data,and/or rotation data. 6 Specifically, transducer 108 is configured tooutput the data during a surgical procedure. In some embodiments,transducer 108 can output data regarding first portion 102 relative tosecond portion 112. By way of example, transducer 108 can be configuredto output data, such as for example, a force generated between firstportion 102 and second portion 112, a position or displacement of firstportion 102 relative to second portion 112, and/or movement of firstportion 102 relative to second portion 112 as the joint in which it ispositioned rotates through a range of motion. In some embodiments,transducer 108 can output a plurality of data signals in absolute terms,as a function of time, and/or as a function of the distance traveled,e.g. range of motion of a joint. Said another way transducer 108 canoutput data at predetermined intervals, such as for example, every onesecond. In other embodiments, the interval can be longer or shorter. Inother embodiments, transducer 108 can continuously output data.

Transducer 108 can be operatively coupled to and configured to outputdata to computer system CS. Computer System CS can be a known computersystem that can include a processor 110, a memory 120, input/outputdevices, including an output module 130, and a communications module140. The processor 110 can be a general-purpose processor or otherprocessor configured to execute one or more instructions. In someembodiments, the processor 110 can alternatively be anapplication-specific integrated circuit (ASIC) or a field programmablegate array (FPGA). The memory 120 can be any fixed or removable memory,such as a Random Access Memory (RAM), Read Only Memory (ROM), a harddisk drive, a solid-state drive (SSD), an optical drive, a flash memorydrive, other removable media. The output module 130 can be ahardware-based and/or software-based module (executing in hardware)configured to output data. For example, the output module 130 can be ahardware module (e.g., a graphics card) operatively coupled to asoftware module (e.g., a video driver). In the example, the outputmodule 130 can be operatively and/or physically coupled to a visualdisplay device, such as a monitor, television, projector, or otherdisplay screen or device. Alternatively, the output module 130 can be ahardware and/or software module configured to output an audio or tactileoutput representing data and/or media. In some embodiments, the outputmodule 130 can be configured to output any combination of audio, video,graphical, or tactile feedback and/or output. More specifically, theoutput module 130 can be configured to output information associatedwith a recommended course of action for a surgical procedure based onthe data received from the transducer 108. In some embodiments, theoutput module 130 can output the recommendations in response to one ormore messages, data frames, data packets and/or other informationreceived from the transducer. In some embodiments, the output module 130can be configured to display any of the above-described information as achart, graph, animation, or other graphical figure or resource. In someembodiments, the output can drive an actuator to cause movement of theportions of the knee balancing apparatus to which it is coupled.

For example, computer system CS can be configured to receive the datafrom transducer 108 and can generate a signal indicative of recommendedaction to balance the joint. Said another way, the signal can indicateto a surgeon to make a specific bone cut and/or loosen and/or tightenone or more connective tissues associated with the joint. In someembodiments, the actuator can receive the signal from the computersystem and can move first portion 102 relative to second portion 112 tosimulate the results of the recommended action.

Communication module 140 can be a hardware-based and/or software-basedmodule (executing in hardware) configured to exchange information withone or more transducers. More specifically, the communication module 140can include one or more network communication cards, drivers and/orother hardware and/or software modules configured to send information toand/or receive information from a network and/or one or more server orclient devices. Thus, in some embodiments, the communication module 140can communicate across a network with the transducer(s) 108 andactuators. In some embodiments, the computer system CS can be acentralized system in communication with the transducer(s) 108 andactuators and a remote graphical display (i.e., the display in theprocedure room during the surgical procedure. In such embodiments, thecomputer system CS can be used to communicate with multipletransducers/actuators in separate procedure rooms either simultaneouslyor serially.

The network across which the computer system CS communicates can be anycomputer network configured to receive and send information between eachor any of the peripheral device transducers 108, actuators, and thecomputer system CS. The network can include one or more computerdevices, such as switching, routing, storage and/or other devices. Insome embodiments, the network can be a local area network (LAN), widearea network (WAN), organization intranet, or the Internet.

FIGS. 3-6 depict examples of implementations of a joint balancingapparatus, specifically a knee balancing apparatus, and methods ofbalancing a knee joint using the knee balancing apparatus. Whilereferences made with respect to FIGS. 3-6 are directed to the kneejoint, apparatus and methods having similar features can be equallyapplicable to other joints as discussed herein. Knee balancing apparatus200 can be a temporary, permanent, or semi-permanent implant configuredto replace at least a portion of a knee joint and to provide data usedto provide real-time feedback to a surgeon during a surgical procedure.The feedback based on the data associated with the procedure can be usedby the surgeon to properly balance the knee joint. After the knee jointis balanced, the knee balancing apparatus 200 can be replaced by apermanent replacement knee (e.g., as illustrated in FIG. 1 ). In someembodiments, only a portion of the knee balancing apparatus 200 isreplaced with a permanent implant, or the entire knee balancingapparatus 200 can remain in place and can function as the permanentreplacement knee joint.

FIG. 3 is a perspective view of a knee balancing apparatus 200, and FIG.4 is an exploded perspective view of knee balancing apparatus 200. Asillustrated, knee balancing apparatus 200 substantially correspondsto/simulates the tibial portion 155 of implant 150 of FIG. 1 . In otherwords, during a knee arthroplasty procedure, the knee balancingapparatus 200 is used to at least temporarily simulate the configurationand position of the tibial portion to ultimately be placed in the knee.Knee balancing apparatus 200 includes a first portion 202, a secondportion 212, an intermediate portion 216, and four transducers andco-located actuators 208A, 208B, 208C, and 208D (collectively“transducers/actuators 208”). While depicted in FIG. 3 and FIG. 4 asincluding four transducers/actuators 208, in some embodiments, kneebalancing apparatus 200 can include more or fewer transducers/actuators208 or one or more arrays of transducers/actuators 208. In someembodiments, the apparatus includes only transducers 208 and need notinclude actuators.

First portion 202 is configured to be coupled to a proximal portion of atibia (represented by dashed lines in FIG. 3 ). In some embodiments,first portion 202 can be coupled to the proximal portion of a tibiasubstantially flush with the proximal portion of the tibia. In suchembodiments, first portion 202 can be held in place by a temporary orpermanent adhesive, and/or another temporary or permanent fastener.First portion 202 includes a mount 204 configured to extend from firstportion 202 and into the proximal portion of the tibia. Mount 204 can beshaped to correspond to a cavity formed in the 9 proximal portion of thetibia. The mount can be held in place by a temporary or permanentadhesive, by friction within the cavity, and/or by another temporary orpermanent fastener. In some embodiments, the mount can be permanentlycoupled to, and/or monolithically formed with, first portion 202. Inother embodiments, the mount can be removably coupled to first portion202. In some embodiments, the mount can be a first mount, and the firstmount can be used during a balancing procedure on a knee joint, and thefirst mount can be replaced by a second mount, during and/or after thebalancing procedure. The second mount is configured to remain in theknee joint after the balancing procedure. First portion 202 includes aproximal surface 206. Proximal surface 206 is configured to beoperatively coupled to transducers/actuators 208 and intermediateportion 216.

Second portion 212 is configured to be coupled between first portion 202and a distal portion of a femur (not shown in FIGS. 3 and 4 ). In someembodiments, second portion 212 can be slidably coupled to the distalportion of the femur. For example, second portion 212 can move relativeto the distal portion of the femur and can maintain a point of contactwith the distal portion of the femur, and the point of contact betweenthe distal portion of the femur and second portion 212 can change as theproximal portion of the tibia moves relative to the distal portion ofthe femur. In some embodiments, the distal portion of the femur can bein direct contact with second portion 212. In other embodiments, acontact or interface portion (not shown in FIGS. 3 and 4 ) can bedisposed between the distal portion of the femur (or a femoral portionof an implant) and the second portion 212 (i.e., similar to theconventional configuration illustrated in FIG. 1 ). In such embodiments,the femoral portion can be fixedly coupled to the distal portion of thefemur, and the contact or interface portion can be coupled to secondportion 212. The contact portion of the second portion 212 can include alayer of material, such as polymeric material, configured to reducefriction between the contact portion and the femoral portion of theimplant. In some embodiments, the shape of the second portion 212 isconfigured to conform to the shape of the permanent implant that will beput in place during the surgical procedure. In other words, the secondportion can be configured to mimic the shape of the interface portion ofthe ultimate implant.

In some embodiments, second portion 212 defines an aperture 220configured to receive a bearing 218 of intermediate portion 216. Secondportion 212 can include a distal surface (not shown in FIGS. 3 and 4 )configured to be operatively coupled to transducers 208.

Intermediate portion 216 and bearing 218 are disposed between firstportion 202 and second portion 212. Intermediate portion 216 is fixedlycoupled to first portion 202 and movably coupled to second portion 212.In this manner, intermediate portion 216 is configured to restrict,limit, or otherwise define, the movement of first portion 202 relativeto second portion 212. Said another way, intermediate portion 216defines the ranges of motion of second portion 212 relative to firstportion 202. A portion of intermediate portion 216 is disposed withinbearing 218 and within second portion 212. Bearing 218 allowsintermediate portion 216 to have a greater or lesser range of motionwithin aperture 220 of second portion 212. In this manner, changing thecharacteristics of bearing 218 can increase or decrease the range ofmotion of intermediate portion 216 within aperture 220 of second portion212, and subsequently can increase or decrease the range of motion ofsecond portion 212 relative to first portion 202. In some embodiments,there are multiple intermediate portions 216. In other embodiments,there are no intermediate portions 216. In other embodiments, there isan intermediation portion formed by, or formed with transducer/actuator208. In some embodiments, the intermediate portion 216 is instrumentedto measure displacement and rotation, or can be actuated to controldisplacement and rotation similar to the manner described in connectionwith the transducers/actuators 208 herein.

Transducers/actuators 208 are configured to output data associated withknee balancing apparatus 200. Transducers/actuators 208 are disposedbetween first portion 202 and second portion 212. Transducers/actuators208 can each include a fixed portion coupled to one of first portion 202or second portion 212, and can each include a movable portion coupled tothe other of first portion 202 or second portion 212. The movableportions of transducers/actuator 208 can be movable relative to thefixed portions of transducers/actuators 208. In some embodiments, thefixed portions of transducers/actuators 208 can be fixedly coupled toone of first portion 202 and second portion 212. In some embodiments,the movable portions of transducers/actuators 208 can be slidablycoupled to one of first portion 202 and second portion 212. Examples oftransducers suitable for use with the apparatus 200 include the NKInstrumented Tibial Plateau available from NK Biotechnical, Minneapolis,Minn. While transducers/actuators 208 are described as a singlecomponent, it should be understood that separate components may beutilized (i.e., physically distinct and separate components).

Transducers/actuators 208 are configured to output data during asurgical procedure, such as for example, force data (e.g., magnitude anddirection), position data, displacement data, and/or data associatedwith the relative position of the first portion 202 with respect to thesecond portion 212 as the apparatus 200 rotates through a range ofmotion during a surgical procedure. In some embodiments,transducers/actuators 208 can output a plurality of data signals inabsolute terms, as a function of time, and/or as a function of thedistance traveled, e.g. range of motion of a joint. Said another way,transducers/actuators 208 can output data at predetermined intervals,such as for example, every one second. In other embodiments, theinterval can be longer or shorter. In other embodiments, thetransducers/actuators 108 can continuously output data as a procedure isperformed and during movement of the tibia through its full range ofmotion. Each of transducers/actuators 208 can output different databased at least on the location of the transducer/actuator relative toeach of the other transducers/actuators 208 and the forces impartedthereon. By way of example, if a force indicated in the location ofarrow AA in FIG. 4 is greater than a force indicated in the location ofarrow BB in FIG. 4 , transducer/actuator 208A and transducer/actuator208B will output force data indicating a first force or forces, andtransducer/actuator 208C and transducer/actuator 208D will output forcedata indicating a second force or forces, less than the first force orforces.

Transducers/actuators 208 are configured to output data to a computersystem (not shown in FIGS. 3 and 4 ) as discussed herein. The computersystem can be configured to receive the data from transducers/actuators208 and can generate a signal indicative of a recommended action tobalance the knee joint. Said another way, the signal can indicate to asurgeon to make a specific bone cut and/or loosen one or more connectivetissues associated with the knee joint.

In some embodiments, the first portion 202 and the second portion 212are spaced parallel to one another at a known distance (e.g., 3-5 mm)and the forces are measured. As discussed in greater detail herein,based on the force information provided by the transducers and thepredetermined distance between the first portion and the second portion,a recommended surgical procedure can be generated. With continuedreference to the example above, the computer system can make arecommended action designed to reduce and/or increase the force AAand/or the force BB such that the force imparted between first portion12 202 and second portion 212 is balanced (i.e., the same across theentire area between the two portions).

The computer system includes an algorithm, discussed in detail herein,designed to interpret the data received from the transducers in making arecommendation for a surgical procedure to correct any perceivedimbalance. The algorithm is configured to account for the force datathroughout a range of motion of the tibia. In some embodiments, arecommended surgical correction is not provided until the knee joint ismoved through the range of motion. In some embodiments, the transducers208 are configured to detect when the range of motion is complete. Inother embodiments, a user can manually indicate when the transducersshould start and stop measurement.

In some embodiments, the algorithm is configured to account for datarelevant to the body of the person into which the implant is beingplaced. For example, the algorithm can be programmed to account for anyone or more of several factors including body weight, height, gaitcycle, leg height/length, bone malformations, soft tissue/muscledefects, neurological disorders, age, gender, activity level, etc.

In some embodiments, transducers/actuators 208 can receive a signal fromthe computer system and can be actuated to cause first portion 202 tomove relative to second portion 212 to simulate the recommendedcorrective action. With continued reference to the example above, insome embodiments transducers/actuators 208 can receive the signalindicative of the recommended action from the computer system and themovable portions of one or more of transducer/actuator 208A,transducer/actuator 208B, transducer/actuator 208C, and/ortransducer/actuator 208D, can move relative to the fixed portion of itsrespective transducer/actuators 208 to simulate the results of therecommended action. In other words, in a situation where the recommendedsurgical correction is to change the angle of, for example, a particularbone cut, the transducers can actuate to cause the second portion 212 tomove to a position simulating that angle (e.g., shorten one or moretransducers).

FIG. 5 is a schematic illustration of a knee balancing apparatus 300 anda knee joint in a first configuration (e.g., near maximum flexion) andFIG. 6 is a schematic illustration of knee balancing apparatus 300 withthe knee joint in a second configuration (e.g., near maximum extension).Components of knee balancing apparatus 300 can be similar to, and havesimilar functions as, the corresponding components in knee balancingapparatus 13 200 and joint balancing apparatus 100. By way of example, afirst portion 302 of knee balancing apparatus 300 can be similar inconfiguration to first portion 202 and first portion 102.

Knee balancing apparatus 300 includes first portion 302 including amount 304, the first portion coupled to a tibia 332, and a secondportion 312 slidably coupled to a femoral portion 336, and disposedbetween second portion 312 and a femur 334. Knee balancing apparatus 300can include an intermediate portion (not shown in FIGS. 5 and 6 ) and atransducer (not shown in FIGS. 5 and 6 ) similar to that describedabove. Knee balancing apparatus 300 includes femoral portion 336 that isfixedly coupled to a femur 334 and is slidably coupled to second portion312.

The knee joint includes a range of motion represented, at the beginningand end of the range of motion, by angle A and angle B, respectively.Angles A and B are the angles between a tibia centerline TCL and a femurcenterline FCL. The complete range of motion of the knee joint can be,for example, from the smallest angle B or the greatest angle A to theother of the smallest angle B or greatest angle A and back. FIG. 4depicts the knee joint in the first configuration near the greatestangle A and FIG. 5 depicts the knee joint in the second configurationnear the smallest angle B. While FIG. 6 depicts the second position ofthe knee joint as approximately zero degrees, in some embodiments, thesecond position is less than zero degrees. Similarly, the greatest angleA, or flexion, of the knee joint can be greater or less than shown. Asthe knee joint is moved, for example, as the tibia 332 moves relative tofemur 334 from the first configuration to the second configuration, thetransducer outputs data, such as for example, force data, position data,displacement data, and/or rotation data to a computer system asdiscussed above. The transducer outputs data at predetermined intervals,such as for example, every 1 second. In other embodiments, the intervalcan be longer or shorter. In other embodiments, the transducer cancontinuously output data. The computer system can generate a signalindicative of a recommended action and output that signal for receiptand consideration by a user. In some embodiments, the signal indicativeof the recommended action can be output directly to the knee balancingapparatus 300.

In some embodiments, the computer system generates a signal indicativeof a recommended action prior to the knee joint finishing the range ofmotion. Said another way, and by way of example, a surgeon can beginwith the knee joint in the first configuration at angle A, and can beginto move tibia 332 relative to femur 334 towards the second 14configuration at angle B. In this example, the transducer can begin tooutput data prior to, during, or after the relative motion begins. Thecomputer system receives the data and generates a signal indicative of arecommended action prior to the knee joint reaching the secondconfiguration at angle B. In other embodiments, the computer systemcollects data associated with the movement of the tibia through itsentire range of motion. In some embodiments, the computer system outputsmore than one possible recommended corrective surgical procedure. Inother words, the output from the computer system can be a recommendationto loosen a particular soft tissue (e.g., ligament) and/or to change theangle of a bone cut.

As discussed above, and with reference to FIG. 12 , an algorithm 900 isoperative to interpret the data received from the transducers in makinga recommendation for a surgical procedure to correct any perceivedimbalance. In some embodiments, the algorithm incorporates, for example,heuristic rules, computer simulation and an experimental data bank toaccomplish its intended functionality.

Heuristic rules incorporate certain inputs acquired using the apparatusdescribed herein, inputs from additional sources, as well as certainoutputs associated with a joint balancing procedure. For example, aninput includes data associated with bone geometry from, for example, apreoperative CT or MRI scan, ultrasound or other imaging modality.Another input includes data associated with an angle between adjacentbony structures (e.g., the angle between femoral and tibial bone shafts)as measured using any device such as surgical instruments, computeraided navigation or robotic systems. A further input includes dataassociated with an angle between bone cuts (e.g., femoral and tibialbone cuts) using joint balancing apparatus (100, 200, etc.) describedherein. Additional inputs include force versus displacement data in, forexample, knee extension and flexion.

Outputs associated with the apparatus include, for example, surgicalrecommendations associated with the received inputs. For example, ifvarious force values are received such that a determination is made thatthe forces are balanced mediolaterally, but tight in flexion and inextension, then a recommended output would be, for example to cut morebone from the proximal tibia (e.g., in a knee balancing situation). Theamount of bone to be cut is calculated from the force versusdisplacement data collected in extension and flexion. If the forces areacceptable and the joint is balanced mediolaterally in flexion, buttight in extension, then a recommended output would be to cut more bonefrom the distal 15 femur (e.g., in a knee balancing situation). Theamount of bone to be cut is calculated from the force versusdisplacement data collected in extension.

The algorithm includes/relies on computer simulation of a procedureassociated with real time events (i.e., during a surgical procedure)and/or a database of simulated procedures. During a surgical procedure,for example, inputs are received similar to the manner described above.For example, relevant bone geometry is obtained from a preoperative CTscan. Additional data associated with bone geometry can be obtained fromreadings/measurements from devices such as surgical instruments,computer aided navigation, or robotic systems. A model of the implantsto be used in the surgical procedure area constructed using computeraided design (CAD) data. The simulated/model implants are positionedbased on the digitized data obtained from the surgical navigationinstruments. Ligament attachment locations for the simulation areobtained by digitizing landmarks using surgical navigation instrumentsor from preoperative or intraoperative imaging. Force versusdisplacement data is collected for the joint (e.g., a knee joint) duringflexion and extension.

The computer simulation relies on computer models created using varioustechniques. For example, a model of the forces across the articularsurfaces of the implants can be derived from calculations utilizingrigid bodies to represent bone and implants and using springs torepresent ligaments. The spring attachments, lengths, and stiffnessvalues can be refined to match force displacement data collected by thesensors/transducers during joint flexion and extension. From the springlengths and stiffnesses, angle of bone cuts, and angle of thetibiofemoral shaft, corrections to bone cuts and ligaments can becalculated.

In some embodiments, a simulation database or databank can be generated.The database (or atlas) can include a variety of femur bones and tibiabones. For example the database can include bones of varying sizes(e.g., very small, small, medium, large, very large) and can beassociated with a variety of factors such as, for example, demographicfactors (e.g., gender, race, bone structure, etc.). A model of therelevant associated implants can be constructed from CAD data asdiscussed above. Combinations of implant position, implant rotation andligament tightness can be created for reference.

A computer model is created and a model of the forces across thearticular surfaces of the implants can be derived from calculationsutilizing rigid bodies to represent bone and implants and using springsto represent ligaments. During a surgical procedure, the 16 force data,etc. that is collected is compared with data from the simulationdatabase. The implant position, rotation and ligament tightnesscondition from the database that most closely matches the intraoperativedata is identified. In some embodiments, the identification is manual.In other embodiments, the identification is automatic.

The implant position, rotation, and ligament tightness conditions areutilized to calculate the amount of correction to the bone cuts or theamount of ligament release or tensioning that is required. Based on thecalculations, a recommendation is provided to make the appropriatecorrection when necessary.

In some embodiments, the algorithm includes an experimental database.The database includes data such as, for example, force displacement datacollected intraoperatively using the joint balancing device as discussedherein. For example, the data can include force data from a kneebalancing device collected intraoperatively during a knee arthroplasty.Any corrections made intraoperatively would be documented. Forcedisplacement data collected after each correction is collected/enteredinto a database to supplement or replace the simulation databasediscussed above. In some embodiments, the data is collected duringcadaver-based surgical procedures.

The force displacement data collected during a subsequent procedure iscompared to data collected in the experimental database. Based on thecalculations, a recommendation is provided to make the appropriatecorrection (e.g., amount of correction to bone cuts and/or amount ofligament release or tensioning) when necessary.

FIG. 7 is a front view of a joint balancing apparatus 400 according toan embodiment, and FIG. 8 is a front view of a joint balancing apparatus500 according to an embodiment. Joint balancing apparatus 400 and jointbalancing apparatus 500 can be similar to joint balancing apparatus 100,knee balancing apparatus 200 and knee balancing apparatus 300. In thismanner, components of joint balancing apparatus 400 and joint balancingapparatus 500 can be similar to and have similar functions as thecorresponding components in knee balancing apparatus 300, knee balancingapparatus 200, and joint balancing apparatus 100. By way of example, afirst portion 402 of knee balancing apparatus 400 and a first portion502 of knee balancing apparatus 500 can be similar in configuration tofirst portion 202 and first portion 102. While a front view isillustrated in FIG. 7 , it should be understood that sensors/transducersassociated with movement of the knee-balancing device in 6 degrees 17 offreedom is contemplated. In other words, the transducers can also detectanterior/posterior movement, medial/lateral movement, translation androtation.

Joint balancing apparatus 400 includes first portion 402, a secondportion 412, an intermediate portion 416, and two transducers 418. Whiledepicted in FIG. 7 as including two transducers 408, in someembodiments, joint balancing apparatus 400 can include more or fewertransducers 408. In contrast to intermediate portion 216 of kneebalancing apparatus 200, intermediate portion 416 extends around theperimeter of the apparatus 400. Intermediate portion 416 can be fixedlycoupled to first portion 402 and second portion 412. In someembodiments, intermediate portion 416 can extend around first portion402 and second portion 412, and, in this manner, can define a fullyenclosed volume between first portion 402 and second portion 412. Inother embodiments, intermediate portion 416 can extend around only aportion of first portion 402 and second portion 412, and, in thismanner, can define a partially enclosed volume between first portion 402and second portion 412. In still other embodiments, intermediate portion416 can include a plurality of intermediate portions 416 each of whichextend around a portion of first portion 402 and second portion 412 tocombine to either fully or partially define a volume between firstportion 402 and second portion 412. Depending on the portion of theapparatus 400 around which the intermediate portion 416 extends, therelative movement of the first portion 402 and the second portion 412can be defined. Additionally, depending on the material properties(e.g., elasticity) of the intermediate portion 416, the relative motionof the first portion 402 and second portion 412 can be dictated. Asshown in FIG. 7 , transducers 408 are disposed within the volume betweenfirst portion 402 and second portion 412. While shown as including onlytransducers 408, joint balancing apparatus 500 can also includeactuators as described herein.

Joint balancing apparatus 500 includes first portion 502, a secondportion 512, an intermediate portion 516, and two transducers 508. Whiledepicted in FIG. 8 as including two transducers 508, in someembodiments, joint balancing apparatus 500 can include more or fewertransducers 508. As shown in FIG. 8 , first portion 502 includes a mount504 configured to be disposed in a cavity within a first bony structure,and intermediate portion 516 is substantially linear in configurationand is configured to be at least partially disposed within an aperture520 of second portion 512. While shown as including only transducers508, joint balancing apparatus 500 can also include actuators asdescribed herein.

FIG. 9 is a front cross-sectional view of an example of a transducer 608in a first configuration, and FIG. 9 is a front cross-sectional view oftransducer 608 in a second configuration. Transducer/actuator 608 can besimilar to any of transducers 108, 208, 308, 408, or 508. In thismanner, components of transducer/actuator 608 can be similar to and havesimilar functions as the corresponding components in any of transducers108, 208, 308, 408, or 508. By way of example, a fixed portion 646 oftransducer/actuator 608 can be similar in configuration to the fixedportion of transducer 108. Transducer/actuator 608 can include fixedportion 646, a movable portion 642, and an actuation and electronicsassembly (“actuation assembly”) 644.

Fixed portion 646 is configured to be coupled to one of a first portion(not shown) or a second portion (not shown in FIGS. 9 and 10 ) of ajoint balancing apparatus (not shown in FIGS. 9 and 10 ). Fixed portion646 can be coupled permanently or temporarily to the first portion orthe second portion and can be fixed mechanically, magnetically, and/orchemically. In this manner, when the first portion moves relative to thesecond portion, the location of transducer 608/actuator relative tofirst or the second portion can be maintained.

Movable portion 642 is configured to be coupled to the other of thefirst portion or the second portion of the joint balancing apparatus,and is operatively coupled to the fixed portion via the actuationassembly 644. Movable portion 642 can be slidably coupled to the firstportion or the second portion. In this manner, when the first portionmoves relative to the second portion the transducer/actuator 608 canfreely slide about the portion to which movable portion 642 is coupled.

Actuation assembly 644 can include an actuation mechanism (not shown inFIGS. 9 and 10 ) configured to move fixed portion 646 relative tomovable portion 642 in response to a received signal, or plurality ofsignals. A signal can include a signal indicative of a recommendedaction or to simulate that recommended action. The actuation mechanismcan be inflatable, piston-based, spring-based, and/or motor based, andcan be hydraulic, pneumatic, electric, magnetic, thermal, piezoelectricand/or manual. Actuation assembly 644 is configured to output data, suchas for example, force data, position data, displacement data, and/orrotation data relating to the interaction of the first portion relativeto the second portion. The electronics mechanism can be configured tooutput data to a computer system (not shown in FIGS. 9 and 10 ), and toreceive signals from the computer system. The electronics mechanism canoutput data wirelessly or via wire. The electronics mechanism 19 can beconfigured to manipulate the actuation mechanism in response to thereceived signals. In some embodiments, actuation assembly 644 can beconfigured to receive signals indicative of recommended action and/orsimulated recommended action.

By way of a example, transducer/actuator 608 can be in a firstconfiguration. When in the first configuration, fixed portion 646 can befixedly coupled to a first portion of a joint balancing apparatus, andmovable portion 642 can be slidably coupled to a second portion of thejoint balancing apparatus. The distance between a distal surface of thesecond portion and a proximal surface of the first portion can be heighth1. Transducer/actuator 608 can receive a signal indicative of arecommended action and, in order to simulate the results of therecommended action, the actuation mechanism moves movable portion 642relative to fixed portion 646 until the distance between the distalsurface of the second portion and the proximal surface of the firstportion, at the position of transducer 608, can be height h2.

In another example, when in the first configuration, fixed portion 646can be fixedly coupled to a first portion of a joint balancingapparatus, but movable portion 642 may not be slidably coupled to asecond portion of the joint balancing apparatus. The distance between adistal surface of the second portion and a proximal surface of the firstportion is unknown. The actuation mechanism moves movable portion 642relative to fixed portion 646 until fixed portion 646 is slidablycoupled to the second portion. In some embodiments, the actuationassembly can cause the actuation mechanism to move movable portion 642relative to fixed portion 646 until fixed portion 646 is slidablycoupled to the second portion and continue to actuate movable portion642 until a force between the first portion and the second portion issubstantially at a predetermined value, or within a predetermined range.In such embodiments, the predetermined value can be an expected range ofa stable joint.

In some embodiments, each of a plurality of transducers/actuators 608can be actuated such that the output data of each of the transducersindicates substantially the same force between the first portion and thesecond portion, and the output data also indicates the height of each ofthe transducers 608 at the predetermined force. The output data isanalyzed and/or interpreted via an algorithm and can result in arecommended action that may result in a change in height of one or moreof transducers/actuators 608. By way of example, a firsttransducer/actuator may be actuated until the force between a firstportion and a second portion at the location of the first transducer isX, and, at force X the first transducer/actuator height can be h1. Asecond transducer/actuator may be actuated until the force between a 20first portion and a second portion at the location of the secondtransducer/actuator is X, and, at force X the second transducer/actuatorheight can be h2. Each of the first transducer/actuator and the secondtransducer/actuator can output force and height data to a computersystem, and the computer system can generate a signal indicative of arecommended action based on that data. The first transducer/actuator andthe second transducer/actuator can receive the signal from the computersystem and can be actuated to simulate a surgical procedure to simulatethe results of the recommended action. In some embodiments, thesimulated procedure can include manipulating other transducers/actuatorsto increase or decrease the height of the first transducer/actuatorand/or second transducer/actuator while maintaining the force betweenthe first portion and second portion. In some embodiments, known forcesare applied to simulate various conditions and monitor thebehavior/performance of the apparatus under those conditions (i.e.,standing, walking, running, jumping, etc.).

In some embodiments (not illustrated) the transducers/actuator arereplaced by a sheet or layer of piezoelectric material configured toperform in substantially the same manner as described with respect tothe transducers/actuators. The piezoelectric material may cover all orjust a portion or certain portions of the second portion of thebalancing apparatus. In some embodiments, the piezoelectric material isconfigured such that a movable second portion is not required, butrather the piezoelectric material is sufficiently flexible enough to bedisplaced a sufficient amount.

In some embodiments, each of a plurality of transducers/actuators 608can be actuated such that the output data of each of the transducersindicates substantially the same distance between the first portion andthe second portion, and the output data also indicates the force data ofeach of the transducers/actuators 608. The computer system can analyzethe output data and can recommend an action that may result in a changein force between the first portion and the second portion at thelocation of one or more of transducers/actuators 608. By way of example,a first transducer/actuator may be actuated until the distance between afirst portion and a second portion at the location of the firsttransducer/actuator is h2 (or some other height), and the force betweenthe first portion and the second portion at the location of the firsttransducer/actuator can be X. A second transducer/actuator may beactuated until the distance between a first portion and a second portionat the location of the second transducer is h2, and the force betweenthe first portion and the second portion at the 21 location of thesecond transducer/actuator can be Y. Each of the firsttransducer/actuator and the second transducer/actuator can output forceand height data to a computer system, and the computer system cangenerate a signal indicative of a recommended action. As the correctiveaction is taken by the surgeon, data is output by thetransducers/actuators to determine if the corrective action waseffective and appropriate real-time updates are provided.

FIG. 11 is a flow chart depicting a method 750 for balancing a jointusing a joint balancing apparatus disclosed herein. Method 750 includesoutputting a signal including a first data set, 752. The first data setcan be associated with at least one of a force, a position, adisplacement or a rotation associated with a joint balancing apparatusdisposed between first a bony structure of the joint and a second bonystructure of the joint. Method 750 includes outputting a second signal,after the performance of at least part of a surgical procedure based onthe first data set, 754. The second signal includes a second data setthat can be associated with at least one of a force, a position, adisplacement or a rotation associated with the joint balancing apparatusafter the performance of at least part of the surgical procedure. Method750 includes moving a movable portion of an actuator, in response to areceived signal, to cause a first portion of an apparatus to moverelative to a second portion of the apparatus, 756.

By way of example, and with reference to FIG. 3 and FIG. 4 , a methodincludes using knee balancing apparatus 200 to balance a knee joint. Themethod can include one or more of transducers 208 outputting a signalincluding a first data set. The first data set can include, for example,the force between first portion 202 and second portion 212 at eachtransducer location. More specifically, transducer 208A and transducer208B can each output a signal indicating a force of X, and transducer208C and transducer 208D can each output a signal indicating a force ofY, force Y being lower than force X. In some embodiments, each of theforces output by the transducers is different. In some embodiments,transducers 208 can output the signal while the knee joint is movingfrom a first position of a range of motion to a second position of arange of motion. In some embodiments, transducers 208 can output aplurality of signals while the knee joint is moving from a firstposition of a range of motion to a second position of a range of motion.The signal including the first data set can be received by a computersystem, and the computer system can generate a signal indicative of arecommended action, for example, a surgical procedure to lower force Xand/or raise force Y. 22 In some embodiments, the recommended action caninclude modifying one or more connective tissues and/or making one ormore bone cuts.

In some embodiments, each of transducers/actuators 208 can receive thesignal from the computer system, and can move each of the movableportions relative to each of the fixed portions, as needed, to simulatethe recommended action. The method can include one or more oftransducers 208 outputting a second signal including a second data set.The second data set can include, for example, the force between firstportion 202 and second portion 212 at each transducer location, aftermoving the movable portions of the transducers 208 relative to the fixedportions of the transducers/actuators 208. More specifically,transducer/actuator 208A and transducer/actuator 208B can each output asignal indicating a force of X, and transducer/actuator 208C andtransducer/actuator 208D can each output a signal indicating a force ofY, force Y being substantially the same as force X. In some embodiments,transducers/actuators 208 can output the second signal while the kneejoint is moving from a first position of a range of motion to a secondposition of a range of motion. In some embodiments,transducers/actuators 208 can output a plurality of second signals whilethe knee joint is moving from a first position of a range of motion to asecond position of a range of motion. In this example, because the forceX and the force Y are substantially the same, the surgeon can completethe recommended action.

Once the surgeon is satisfied that the knee is appropriately balanced(i.e., the soft tissue as well as the hard tissue), the apparatus 200(similarly 100, 300, 400, 500, etc.) can be removed from the body. Thesurgeon can subsequently place a more permanent or final implant in itsplace. The dimensions and physical characteristics of the final implantare substantially the same as the balancing apparatus. Thus, when thefinal implant is in position, the knee remains properly balanced.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Where methods described above indicate certain eventsoccurring in certain order, the ordering of certain events can bemodified. Additionally, certain of the events can be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above. Although various embodiments have beendescribed as having particular features and/or combinations ofcomponents, other embodiments are possible having a combination of anyfeatures and/or components from any of embodiments where appropriate. Byway of 23 example, the examples and embodiments described with referenceto transducer 608 can be applicable to the other transducers describedand to the associated joint balancing apparatus.

Some embodiments described herein relate to a computer storage productwith a non-transitory computer-readable medium (also can be referred toas a non-transitory processor-readable medium) having instructions orcomputer code thereon for performing various computer-implementedoperations. The computer-readable medium (or processor readable medium)is non-transitory in the sense that it does not include transitorypropagating signals per se (e.g., a propagating electromagnetic wavecarrying information on a transmission medium such as space or a cable).The media and computer code (also can be referred to as code) can bethose designed and constructed for the specific purpose or purposes.Examples of computer-readable media include, but are not limited to:magnetic storage media such as hard disks, floppy disks, and magnetictape; optical storage media such as Compact Disc/Digital Video Discs(CD/DVDs), Compact Disc-Read Only Memories (CDROMs), and holographicdevices; magneto-optical storage media such as optical disks; carrierwave signal processing modules; and hardware devices that are speciallyconfigured to store and execute program code, such asApplication-Specific Integrated Circuits (ASICs), Programmable LogicDevices (PLDs), Read-Only Memory (ROM) and Random-Access Memory (RAM)devices.

Examples of computer code include, but are not limited to, micro-code ormicroinstructions, machine instructions, such as produced by a compiler,code used to produce a web service, and files containing higher-levelinstructions that are executed by a computer using an interpreter. Forexample, embodiments can be implemented using Java, C++, or otherprogramming languages (e.g., object-oriented programming languages) anddevelopment tools. Additional examples of computer code include, but arenot limited to, control signals, encrypted code, and compressed code.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, notlimitation, and various changes in form and details can be made. By wayof example, while knee balancing apparatus 200 is described as having apost-shaped intermediate portion 216, in some embodiments, kneebalancing apparatus 200 can include an intermediate portion, similar tointermediate portion 416 shown in FIG. 5 . Any portion of the apparatusand/or methods described herein can be combined in any combination,except mutually exclusive combinations. The embodiments 24 describedherein can include various combinations and/or sub-combinations of thefunctions, components and/or features of the different embodimentsdescribed.

In some embodiments, the balancing apparatus does not include anintermediate portion. In such an embodiment, the transducers themselvesact to limit/define the relative movement of the second portion of theapparatus with respect to the first portion of the apparatus.

1.-17. (canceled)
 18. A joint balancing device configured to betemporarily disposed within a joint of a patient, comprising: a firstportion configured to contact a first bony structure of the joint; asecond portion opposite the first portion, wherein the second portion isconfigured to contact a second bony structure of the joint that isopposite the first bony structure of the joint; a plurality oftransducer/actuators disposed within a volume between the first portionand the second portion, wherein each of the transducer/actuatorscomprises a transducer and an actuator that are co-located with oneanother, and wherein the plurality of transducer/actuators are spacedapart from one another such that each actuator causes relative movementbetween the first portion and the second portion at a locationcorresponding to each actuator, and such that each transducer capturesdata relating to the relative movement at a location corresponding toeach actuator, wherein the data includes at least one of force data,position data, displacement data, or rotation data; and at least onebearing configured to control a range of motion of the second portionrelative to the first portion.
 19. The joint balancing device of claim18, wherein the plurality of transducer/actuators comprises fourtransducer/actuators.
 20. The joint balancing device of claim 18,wherein the first portion comprises a mount extending in a directionaway from the second portion and configured to extend into a cavitywithin the first bony structure.
 21. The joint balancing device of claim20, wherein the mount is removably coupled to the first portion.
 22. Thejoint balancing device of claim 18, wherein the bearing is configured tohave characteristics of the bearing changed to thereby either increaseor decrease the range of motion of the second portion relative to thefirst portion.
 23. The joint balancing device of claim 18, wherein thebearing is received within an aperture formed within the second portion.24. The joint balancing device of claim 23, wherein the first portioncomprises an intermediate portion that contacts the bearing.
 25. Thejoint balancing device of claim 24, wherein a portion of theintermediate portion is disposed within the bearing to thereby enablethe bearing to control the range of motion.
 26. The joint balancingdevice of claim 18, wherein each of the plurality oftransducer/actuators is configured to be communicatively coupled to acomputer system.
 27. The joint balancing device of claim 18, whereineach of the plurality of transducer/actuators is coupled to at least oneof the first portion or the second portion.
 28. The joint balancingdevice of claim 27, wherein each of the plurality oftransducer/actuators comprises (1) a fixed portion that is coupled toone of the first portion or the second portion and (2) a movable portionthat is coupled to the other one of the first portion or the secondportion.
 29. The joint balancing device of claim 28, wherein the movableportion is slidably coupled to the other one of the first portion or thesecond portion.